Starting from. An Introduction to Computing Science by Jeremy Scott LEARNER NOTES

Transcription

1 Starting from An to Computing Science by Jeremy Scott LEARNER NOTES

2 You have probably already used several computers today without realising it. If you have sent a text, been driven in a car, or checked your watch then you have used a computer. The words you are reading now were typed on a computer. Computers are all around us. Since they affect so many parts of our lives, it is important to understand how they work. What is a computer? A computer is a machine that carries out instructions given to it by a human. Without instructions, computers wouldn t be able to do anything. If this is the case, then what makes them special? Well, computers work faster than humans 1 ; are more accurate than humans; can store huge amounts of information that they never forget. It might seem that computers can do almost anything. However, here are some other important things to remember: Computers don t have brains; they are not cleverer than humans. Computers don t have feelings or common sense. This means that there are lots of everyday tasks that humans can perform that computers still cannot. Write down three everyday tasks that humans perform but computers cannot (or are not very good at) At the time of writing, a modern personal computer could perform over 100 billion calculations every second! Page 5

3 Types of computer Computers come in many shapes and sizes. Computers that most people might recognise include: Desktop A desktop PC (Personal Computer) is designed to sit on top of or under a desk and is used by one person at a time. It is powered by mains electricity and made up of separate devices. Laptop Laptop computers combine all the separate devices of a desktop PC into one unit. This can be carried around and powered by mains electricity or battery. Netbooks and ultrabooks are just smaller, lighter types of laptop. Tablet This has a large, touch sensitive screen which is used with your finger (or sometimes a special pen). It is battery-powered and very portable. Tablets have an on-screen virtual keyboard 2. The personal computers shown above appear in order of oldest to newest types. What does this tell you about the kind of computers people want? 2 The word virtual is used a lot in Computing. It just means not real it s something that s been recreated on a computer. Can you think of any other virtual things you get on a computer? Page 6

4 Other computers that may not be as well-known or recognised by most people include: Mainframe This is a large computer which can take up an entire room. Many users can use it at the same time, each with their own keyboard, mouse and monitor. Mainframes are very expensive and need a team of people to run them. They are owned by large organisations that need to store and process huge amounts of information. Server A server is a computer that provides services for other computers on a network e.g. file server (stores users files) web server (serves out web pages) mail server (provides services) Games console Games consoles are also computers. Most have a disc drive for loading games and a powerful processor to create realistic graphics. Many games consoles can also connect to the Internet, letting users buy games online or compete with other gamers around the world. Page 7

5 Embedded Many devices in your home have an embedded computer a small silicon chip that carries out stored instructions. The modern home has over 100 of these computers, built into devices like a toaster, stereo, washing machine, fridge, TV, etc. A modern car may have another 100 or more embedded computers 3. Write down three devices in your own home that you think might contain an embedded computer (besides those shown above) Smartphone Smart mobile phones like Android and Apple iphone are really pocket computers that can also make phone calls. Many smartphones use large touch screens. This is a good example of convergence where technologies that were previously separate are now combined in one device. Write down three technologies that are combined in a modern smartphone Source: Page 8

6 Parts of a computer A computer is a machine that: takes in information stores this information processes this information and gives this processed information back out. INPUT PROCESS OUTPUT STORAGE Write down inputs and outputs for the following activities on different types of computers. When you have finished, create an extra one of your own: Input(s) Output(s) Playing a video game Move game controller Click buttons Character moves Menu selections made Surfing the WWW Making a phone call Watching TV Page 9

7 There are two main parts to a computer: hardware and software. Hardware Hardware means computer equipment. A single piece of hardware is called a device. There are four main types of device in a computer: Input device Central Processing Unit (CPU) Output device Storage device used to put data into the computer where the computer carries out the instructions given by the programs. The faster the processor, the faster your computer will work. used for data coming out of the computer used to store programs and data. It is where you save your work on to. Put simply if you can touch it, it s hardware. Decide if the following devices are input, output or storage devices then put each one into the correct column. The first three have been done for you. keyboard; hard disc drive; monitor; speaker; scanner; printer; mouse; DVD drive; microphone; memory stick; game controller; smartphone touch screen; memory card Input Device Storage Device Output Device keyboard hard disc drive monitor Page 10

8 Software A computer can perform different tasks, depending on the instructions it is given. A list of instructions is called a program. Without a program to tell it what to do, a computer would just be a (useless) collection of hardware devices. Software is the name given to programs and the information they use. Complete the table below of ten different jobs you can do on a computer and the name of a software package that lets you do it. Task Browse the World Wide Web Play games Edit a movie Software package Internet Explorer Angry Birds imovie Page 11

9 Programming languages Computers follow instructions given to them by humans. They can solve only the problems that people tell them to solve. To tell a computer what to do, you must know what problem you want to solve and have a plan for solving it. Unfortunately, these instructions can t just be given to the computer in normal English. A computer can perform tasks very quickly, but it is not intelligent like we are. A computer will do: only what it is told and exactly what it is told. This means that computer programs have to be written in a very precise way, according to strict rules. There must be no confusion over what instructions mean. A set of instructions and rules that a program can be written in is called a programming language. Page 12

10 Programming in Scratch Programming in Scratch The rest of this course will focus on how to write computer programs. You will be using Scratch, created by MIT (Massachusetts Institute of Technology), one of the USA s leading universities. Scratch is a powerful software development package. It lets you create programs (called projects) that combine sound, graphics and animation. You can upload your projects to the Scratch website and share with other Scratchers around the world. It really is the cat s whiskers! You will learn how to use Scratch through a series of lessons. At the end of each one, there will be some questions which will help to check if you have understood what you have learned. A model of the Scratch cat at MIT Media Lab Page 13